ch17 - applications of immune responses

vaccination and immunization

vaccination: the process/act of giving a vaccine to induce an immune response

• it’s a medical procedure to produce an antigen in the body

• probably had greatest impact on human health of any medical procedures

• prevents diseases which is why it has a great impact

immunization: the response from the body resulting in the development of resistance or immunity against a specific disease

principles of immunization

immunity is acquired naturally or artificially

• naturally: through natural events (infections/disease)

• artificially: through vaccination (medical procedure)

immunity can also be active or passive

• active immunity

  • exposure to an antigen → body produces antibodies and memory cells

• passive immunity

  • body receives pre-made antibodies, not memory cells

one useful distinction:

• natural/artificial describes how immunity is acquired

• active/passive describes who makes the antibodies

types of immunity

natural, active immunity: antibodies and memory cells produced following illness (infections/diseases)

• pathogen enters body

• body produces antibodies and memory cells

artificial, active immunity: acquired through vaccination

• antigen injected into body

• body produces antibodies and memory cells

natural, passive immunity: antibodies made by mother → fetus/newborn

• pregnancy

  • IgG crosses the placenta

• breastfeeding

  • IgA and IgG in breast milk

artificial, passive immunity

• acquired by injection of antibodies

• used to prevent disease before or after exposure

• antiserum (solution of antibodies) or antitoxin (solution of antibodies against a toxin)

  • example: antiserum against rabies; antitoxin against botulism

vaccines and immunization procedures

vaccine: preparation of pathogen or its products

• used to induce active immunity

• result: formation of antibodies and memory cells

  • produces rapid and intense secondary response on subsequent exposure

  • vaccines take advantage of the secondary immune response

widespread immunization → herd/community immunity

• occurs when a majority of the population is immune to a disease

• prevent spread of infectious agent in population due to insufficient susceptible hosts

• responsible for dramatic declines in childhood diseases

  • diseases reappear due to failure to vaccinate

vaccines and immunization procedures part 2*

ideal vaccines should be

• effective and safe, few side effects

• give long lasting immunity

• ideally low in cost, stable, easy to administer

• ex. for covid some people say the vaccine doesn’t work but it’s because the pathogen changes and becomes a new one, its an mRNA vaccine which is why its…

some vaccines routinely given, others only under certain circumstances

importance of childhood immunizations

• prior to vaccinations, many deaths, disabilities

  • many still become ill or die from preventable diseases

    • vaccines victims of their own success → people have false sense of security

    • some parents refuse to vaccinate children, fear harm

    • smallpox has been eradicated from the world

polio

• most dreaded childhood diseases of the 20th century in the US

• virus infects the motor neurons of the brain and spinal cord → paralysis

• vaccines

  • 1955: salk inactivated polio vaccine

  • 1960s: Sabin attenuated oral polio vaccine (OPV)

• 1979: last case of “wild” (not imported) polio in US

  • other cases due to oral polio vaccine (OPV) or imported

  • vaccine risk – 1/2.4 million contract disease → 8-10 cases/year

• 1995: US stopped using Oral polio vaccine (OPV)

due to a successful vaccination program, the United States has been polio-free since 1979

measles in the United States

• Causative agent = measles virus

• Cases greatly decreased after introduction of vaccine in 1960s

• US experiencing record number of measles cases

  • Outbreaks happen when vaccination coverage drops

  • Measles spreads very easily, so low vaccination rates can quickly produce outbreaks

• 2025: 2,289 cases, 3 deaths

• 2026: As 9/24/2026, 3,659 cases, 2 deaths

• majority of people are not vaccinated which is why the cases are so high

US measles cases outbreaks due to importations

• Returning infected U.S. travelers (aged 6–11 months)

• Foreign visitors

• Importations puts unvaccinated populations at risk

  • Those who cannot be vaccinated due to underlying medical conditions

• Infants too young to be vaccinated

  • First MMR vaccine at 12 months

• Community in U.S. where people are unvaccinated

2015:

• 188 cases, 21 states

• Disneyland - Largest outbreak (117 cases, 68%)

• Traveler infected overseas, visited park while infectious

2018-2019 (1,282 cases in2019)

• Biggest outbreaks in New York and New Jersey

• Unvaccinated people in Orthodox Jewish communities

• Due to travelers who brought measles back from Israel

measles outbreak in Texas, 2025*

Outbreak due to unvaccinated travelers getting infected and spreading to unvaccinated population

• 2025: 990 total cases (out of 2,288 cases total in the US)

• 2 deaths (out of 3 total in US)

Why so many cases:

• Low vaccination rate in East Texas

• Majority of victims are unvaccinated

MMR

• Requires >95% coverage for community immunity (herd immunity)

*reasons for not receiving measles vaccine

New California Vaccination Laws

2016: SB 277 became law

• Removes all non-medical exemptions to vaccine requirements for entry into school

• Only exemptions accepted: medical

2019: SB 276 – became law Sept 2019

• Revision to SB277 - seeks to combat fake medical exemptions

• Give state public health officials oversight of

  • Doctors who grant high numbers of medical exemptions for vaccinations

  • Schools with vaccination rates less than 95%

    • 95% needed to provide "community immunity"

types of vaccines - attenuated vaccines

Live/active, weakened form of pathogen

• Advantages: Single doses induce strong, long-lasting immunity

  • Microbes multiplying in body of vaccine recipient → undetectable or mild symptoms

• Disadvantages

  • Can cause disease in immunocompromised individuals and pregnant women

  • Can revert or mutate, become pathogenic

  • Requires refrigeration

• Attenuated vaccines in use

  • MMR, chickenpox (Varicella-zoster), influenza, vaccinia virus (smallpox)

types of vaccines - inactivated vaccines

dead/inactivated

• Advantage: cannot cause infections or revert to pathogenic forms

• Disadvantage: no replication, so no amplification in vivo; immune response is weaker

  • Several booster doses usually needed

  • Often contain adjuvant to enhance immune response

    • Example: FLUAD – inactivated flu vaccine + adjuvant for people 65 yrs and

types of vaccines - nucleic acid vaccines

DNA vaccine - West Nile (for horses)

• mRNA Vaccines - COVID-19

  • Pfizer, 21 days later

  • Moderna, 28 days later

    • Both are 2 doses, with boosters

different types of inactivated vaccines*

Inactivated whole agents - killed organisms or inactivated virus (formalin)

• Preserve surface epitopes

• Hepatitis A, rabies, influenza

Toxoids: toxins treated to destroy toxic part, retain antigenic epitopes

• Diphtheria, tetanus

Subunit vaccines: contain key antigens from pathogen

• Avoids cell parts that may cause side effects

• **hA has so many antigens that it will have a lot of side effects

• Acellular pertussis (aP) vaccine

  • only made to the capsule found on the surface on the outside ***

vaccine safety

No vaccine can be guaranteed to be 100%safe

• Some people have mild side-effects

• Rarely, vaccines can cause the disease

• No medical/scientific proof of MMR vaccines being linked to autism

• Safest and most effective means of preventing infectious disease in children